The primary purpose of the study is to compare the efficacy and safety of 1-alpha-acetylmethadol (LAAM) and methadone in treating heroin addicts in a maintenance program. As a part of a cooperative study, statistical evaluation will be done to determine efficacy by measuring changes in social adjustment, arrest rate, employment, use of illicit drugs and retention rate on the drugs being compared. Safety will be evaluated by monitoring patients for symptoms, signs, and laboratory test value changes. A common protocol will be followed by all cooperating centers, all data collected on standard forms, and all analysis of such data will be done centrally under the direction of NIDA.